Clad power metallurgy article and method for producing the same

ABSTRACT

A clad article of a substrate of one powdered metal that is clad with a second dissimilar powdered metal. A separation layer may be provided between the substrate and the clad layer to separate these layers during consolidation and to facilitate bonding thereof. The consolidation operation may be performed by hot isostatic pressing of the powders within a deformable container.

BRIEF DESCRIPTION OF THE INVENTION

1. Field of the Invention

The invention relates to a clad article of powdered metal and a methodfor producing the same, wherein the substrate and the clad layer areboth of powdered metal of dissimilar composition.

2. Background of the Invention

It is known in the art to produce powder metallurgy clad articles,particularly employing hot isostatic pressing for the production of thesame. Specifically, the known processes are substantially the same withvariations only on where and how the clad metal layer is applied. Forexample, it is known to clad the outside or the inside of a hollow barby hot isostatic pressing. Currently, the substrate for the clad layerhas usually constituted part of the container for the clad powder usedduring hot isostatic pressing.

In more specific applications such as the production of a hollow barused to inject semi-solid material of magnesium and aluminum into a dieassembly, the highly corrosive properties of these materials in asemi-solid state require that the interior of the hollow bar beresistant to this corrosion. Consequently, the interior of these hollowbars for this injection of semi-solid magnesium and aluminum are usuallyof a refractory metal alloy containing, for example, 50% Nb, 30% Ti, 20%W. This alloy does not have sufficient strength or toughness to be usedas a monolithic component. In addition, the cost of a monolithiccomponent of this material would be prohibitive.

Alloy steel is the ideal component for the substrate of this hollow barfor this application. However, in injection applications of semi-solidmagnesium and aluminum, the temperatures employed are about 1200° F.These temperatures are too high for alloy steel to maintain itsstrength. In addition, alloy steel is not sufficiently corrosionresistant with respect to semi-solid magnesium or aluminum. Therefore,the ideal material for this purpose is a nickel base alloy. However,even with nickel base alloys, the hot isostatic pressing practice usedfor cladding may be performed at a temperature sufficiently high suchthat uncontrollable grain growth occurs.

SUMMARY OF THE INVENTION

It is accordingly, a primary object of the present invention to providea powdered metal clad article and method for producing the same, whereinthe cladding operation may be performed efficiently, as by the use ofhot isostatic pressing, to achieve an article constituting a substrateof one powdered metal and a clad layer of a second dissimilar powderedmetal.

A further object of the invention is to provide a clad article of thistype wherein the dissimilar metals may be selected to provide theproperties required for a particular application, for example, a highstrength substrate to which a clad layer of a highly corrosion resistantalloy is bonded.

In accordance with the invention, the clad article thereof comprises asubstrate of one powdered metal and clad layer of a second dissimilarpowdered metal bonded to the substrate to form the final clad article.At least one additional clad layer of an additional dissimilar powderedmetal may also be bonded to the substrate.

A solid metal separation layer may be provided between the substrate andthe clad layer. This metal separation layer may be a bonding agent forbonding the substrate and the clad layer. This metal separation layermay be steel.

The substrate may be a nickel base alloy With the clad layer being arefractory metal alloy, such as an alloy of Nb, Ti, W. Specifically, theclad layer may be of an alloy comprising, in weight percent, about 50%Nb, about 30% Ti, and about 20% W.

The powdered metal of the substrate and the clad layer may be ofprealloyed powder.

The powdered metal of the substrate and the dissimilar powdered metal ofthe clad layer may have a similar packing density.

The clad article may be in the form of a hollow bar. The hollow bar mayhave the clad layer bonded to an interior substrate surface thereof.

In accordance with the method of the invention, the clad article havinga substrate of one powdered metal and a clad layer of a seconddissimilar powdered metal bonded to the substrate may be produced byproviding a deformable container, positioning within the deformablecontainer a layer of powder of the one powdered metal and an adjacentlayer of powder of a second dissimilar powdered metal, and deforming thecontainer to consolidate and bond the one layer and adjacent layer ofpowder to substantially full density to form the clad article. At leastone additional clad layer of an additional dissimilar powdered metal mayalso be bonded to the substrate.

A solid metal separation layer may be positioned between the layers ofpowder within the deformable container to bond the layers duringdeforming of the container.

This separation layer may be steel.

One of the layers may be a nickel base alloy and the second dissimilarpowdered metal layer may be a refractory metal alloy, such as an alloyof Nb, Ti, W and specifically, about 50% Nb, about 30% Ti, and about 20%W.

The powder of each layer may be prealloyed powder.

The powder of each layer may have similar packing density.

The final clad article may be in the form of a hollow cylinder. Thehollow cylinder may have a clad layer bonded to an interior substratesurface thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic showing in vertical cross section of a deformablecontainer in vertical cross section after compaction in accordance withthe invention;

FIG. 2 is an enlarged view of a portion of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the Figures, and specifically with reference to FIG.1, there is shown a deformable container after hot isostatic pressingthereof to produce the clad article in accordance with the invention.This assembly is designated generally as 10.

The assembly 10 includes a deformable container 12, which may be of mildsteel, and a liner 14 which may be of stainless steel or mild steel. Ahollow cylindrical substrate 16, which may be a nickel base alloy, isbonded to an interior clad layer 18, which may be an alloy of Nb, Ti, W.

Consequently, after hot isostatic pressing to consolidate and bond thesubstrate 12 and cladding layer 18, which are prealloyed powderparticles, upon removal of the container 12 a clad article in accordancewith the invention is obtained. The metal separation layer 14 is used toseparate the two dissimilar powdered metal components 16 and 18, as wellas facilitating bonding thereof during hot isostatic pressing.

What is claimed is:
 1. A method of producing a clad article having asubstrate of one powdered metal and a clad layer of a second dissimilarpowdered metal bonded to said substrate to form said clad article, saidmethod comprising: providing a deformable container; positioning withinsaid deformable container a layer of powder of said one powdered metalwhich is a nickel base alloy and an adjacent layer of powder of saidsecond dissimilar powdered metal which is a refractory alloy; anddeforming said container to consolidate and bond said layer of powderand said adjacent layer of powder to substantially full density to formsaid clad article.
 2. The method of claim 1, wherein at least oneadditional clad layer of an additional dissimilar powdered metal isbonded to said substrate in addition to said clad layer of said seconddissimilar powdered metal.
 3. The method of claim 1, wherein a solidmetal separation layer is positioned between said layer of powder andsaid adjacent layer of powder within said deformable container to bondsaid layer of powder and said adjacent layer of powder during saiddeforming of said container.
 4. The method of claim 3, wherein saidseparation layer is steel.
 5. The method of claim 1, wherein said cladlayer is a Nb, Ti, W alloy.
 6. The method of claim 5, wherein saiddissimilar powdered metal of said clad layer is an alloy comprising, inweight percent, about 50% Nb, about 30% Ti, and about 20% W.
 7. Themethod of claim 1, 2 or 3, wherein said powder of said one powderedmetal and said powder of said second dissimilar powdered metal are ofprealloyed powder.
 8. The method of claim 7, wherein said one powder ofsaid one powdered metal and said powder of said second dissimilarpowdered metal have similar packing density.
 9. The method of claim 1, 2or 3, wherein said clad article is a hollow cylinder.
 10. The method ofclaim 9, wherein said hollow cylinder has said clad layer bonded to aninterior substrate surface thereof.